每个标记有一个title属性，这个属性为命令定义一个可读的标题。
Each tag has a title attribute that defines a human readable title for the command.
获取一个值，该值指示该属性是否可读。
Gets a value indicating whether the property can be written to.
用于访问集合对象本身的属性是只读的，而集合本身是可读写的。
The property to access the collection object itself is read-only, the collection itself is read-write.
用于访问集合对象本身的属性是只读的，而集合本身是可读写的。
The property to access the collection object itself is read-only, the collection itself is read-write.
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